I. Field of the Invention
The present invention relates to a construction for supporting the tip member of an ultrasonically reciprocating or vibrating element using flexure supports which are resonantly tuned to the frequency of the reciprocating element.
II. Description of the Prior Art
The invention has application in any construction in which an unattached end of an ultrasonically reciprocating or vibrating elongated member is to be positioned laterally but permitted the greatest possible freedom of movement in the longitudinal direction. A typical form of construction previously used is disclosed in USSR Patent No. 490,959 which discloses a slide member mounted to a frame by means of resilient element in the form of closed oval strip springs joined respectively to the slide member and the frame. Upon gradual movement of the slide member relative to the frame, the resilient elements roll relative to the frame and the slide member. The range of movement of the slide member is said to be about half the straight line surface length of the resilient elements. However, the slide member is attached to the resilient elements thereby reducing its freedom of motion. Furthermore, the slide member is not intended to be moved ultrasonical ly and there is no consideration given in the patent to making the resilient elements resonate in harmony with the slide member.
A specific application for the invention resides in its use in combination with a wiring or wire embedding machine for producing encapsulated circuit boards, or ECBs. An example of such a machine is Multiwire.RTM. 2000 Series Wiring Machine manufactured by the Electronic Equipment Division of Kollmorgen Corporation of Melville, N.Y. A machine of this type utilizes an ultrasonically vibrating stylus to embed insulated copper wires on an adhesive coated substrate to form a circuit board. The wire is advanced under and through a grooved tip of the stylus which serves to locate the wire for placement on the circuit board. The tip of the stylus vibrates vertically at approximately 25K hertz to cause the adhesive under the wire to melt thereby affixing the wire to the substrate. The stylus is supported in a fixed fashion at a nodal point and a toughened plastic bushing is used to support the stylus at the tip end.
Required machining tolerances for the bushing and for the tip member of the stylus, in addition to a requirement to minimize the damping of the stylus, result in a necessary amount of "play" between the stylus tip and the internal diameter of the bushing. This play increases as the bushing wears and is undesirable because it contributes to misregistration of the wire as it is placed on the surface of the circuit board. One possible solution to the problem might be to replace the bushing which serves as a journal bearing with an anti-friction bearing provided with preloaded balls or rollers. However, such an attempted solution would fail because of the extremely high bidirectional speeds and attendant accelerations and decelerations involved. To generate the high accelerations required by the rolling elements would require preloads between the rolling elements and the stylus tip so high that they would cause excessive contact stresses between the rolling elements and the stylus tip.